Table 2.

Kinetic constants for ExoS and ExoT ADP-ribosyltransferase domain activity

	Target	KMεNAD (μM)	KMtarget (μM)	kcat (min−1)	kcat/KM (μM−1 s−1)
ART domains
ExoS233–453	—a	28.6 ± 6.6	n.a.b	9.9 ± 0.72	5.7 × 10−3
ExoS233–453	K-Ras	49.0 ± 9.1	32.2 ± 9.9	7.9 ± 0.5	2.7 × 10−3
ExoS233–453	Rac3	41.7 ± 9.3	11.4 ± 4.6	11.2 ± 0.8	4.5 × 10−3
ExoS233–453	Rnd1	39.9 ± 18.1	4.8 ± 1.9	7.9 ± 1.0	3.3 × 10−3
ExoS233–453	Agmatine	133 ± 14	2760 ± 130	53.5 ± 2.2	6.7 × 10−3
ExoT235–457	Crk	8.2 ± 1.9	16.9 ± 2.6	2.1 ± 0.10	4.3 × 10−3
ExoT235–457	Agmatine	44.4 ± 5.8	660 ± 160	0.24 ± 0.01	0.1 × 10−3
C-terminal deletions
ExoS233–435	—a	61.2 ± 8.9	n.a.	7.2 ± 0.4	1.9 × 10−3
ExoS233–435	K-Ras	37.2 ± 2.2	17.0 ± 3.1	11.7 ± 0.22	5.3 × 10−3
ExoS233–419 c	—a	88.5 ± 11.1	n.a.	n.d.d	n.d.
ExoS233–419 c	K-Ras	96.9 ± 18.1	36.1 ± 15.7	n.d.	n.d.
ExoS-Vis chimaera
SxVis	— a	378 ± 81	n.a.	0.10 ± 0.01	4.4 × 10−5
SxVis	K-Ras	114 ± 19 e	n.d.	0.42 ± 0.03	6.1 × 10−5

Calculated from ADP-ribosyltransferase activities using 14-3-3β as a cofactor (except ExoS-Vis chimaera), εNAD⁺ as a co-substrate, and the indicated substrates (at a concentration near their K_M) as an acceptor for the modification Rate data (n = 2) were converted to concentrations of εNAD⁺ by calibration with εAMP, and fitted to the Michaelis equation. Means ± standard errors are reported

^aGlycohydrolase activity/automodification

^bNot applicable

^cCo-expressed with 14-3-3β

^dNot determined

^eIn the presence of 30 μM K-Ras